The objective of this project is the development of new methods for the analysis of X-ray diffraction data from large macromolecular assemblies that will not crystallize. These methods will be used to obtain clear images of the subcellular structures such as cell membranes, viruses and cytoplasmic assemblies. Our work has shown that there is much more information in diffraction patterns from non-crystalline specimens than is obtained when a pattern is processed by conventional methods. Research will focus on three areas of data analysis: the collection of intensity data to the highest possible resolution; analysis of packing disorder in specimens; and refinement of molecular models and phase determination using continuous data along layer lines in fiber diffraction patterns. The methods will be applied to the analysis of X-ray data from several important molecular systems including gap junctions, filamentous bacteriophage, tobacco mosaic virus and microtubules. Structural studies of gap junctions in different conformational states will provide information about the control of inter-cellular communication; studies on helical viruses will result in detailed pictures of protein-nucleic acid interactions and protein-protein interactions which must govern the assembly of these structures; studies of microtubule structure will contribute to a fundamental understanding of the molecular mechanisms involved in cell division. The molecular systems being studied are representative of a larger group that includes all the sub-cellular assemblies involved in maintaining the structure and growth of normal and malignant cells.